Computer Power Supply Unit in PC | Computer PSU Info Details

You might have heard of the term
“power supply unit” (PSU) or “SMPS” (switch mode power supply) — yes
that’s a part of your computer system, even if you haven’t heard of it.
The power supply is not only one of the most important parts in a PC,
but unfortunately, it’s also the most overlooked one. People brag and
spend hours discussing their PC’s processor speeds, monitor size, amount
of RAM and disk storage but rarely specify the device that powers their
system. there’s no respect for the humble and unglamorous metal box
that sits at a corner of your system.

When
a system is put together to meet the lowest possible price point, what
component do you think the assembler or manufacturer compromises on?
Yes, it’s the power supply unit, and it is that same device which most
often responsible for internal damage in your system, be it burnt
motherboards, CPUs, graphics cards or other components that were killed
due to electrical faults. So you save on the PSU while buying a PC and
pay much more for the mistake later.
Even if people pay little attention to PSU, they are more concerned
about the power rating label that is stuck on them by the manufacturer.
Without regard to whether the power being produced is clean and stable
or whether it is full of noise, spikes and surges. A person building a
new PC should give special emphasis on selecting a power supply to get a
robust and reliable unit. It will ensure peace of mind throughout the
life time of the PC.

Basic functions of a PSU

The basic function of a power supply is to convert the electrical
power available (AC 120V, 50Hz/AC 240V, 50Hz) to that which the computer
circuit can use (DC +3.3V, +5V, +12V). The objective in manufacturing a
power supply is to provide an efficient power source which generates
minimum heat. If you observe a power supply unit, you are sure to notice
that there is a fan built into it. Now that fan throws out hot air from
inside the cabinet thereby keeping the PSU as well as the whole system
cool. The fan diameter typically ranges from 60mm to 200mm or even
larger, depending on the manufacturer. It’s basic logic that larger
diameter fans will throw out more air and thereby keep the system cool,
but efficient PSUs may not need large fans as they generate less heat.
Therefore fan size is not a major criterion while deciding on a PSU.

Voltage Rails

Power is generally supplied to the motherboard over multiple wires
connected to the same source circuit called rail or tap inside the power
supply. Each rail can be imagined to be a separate power circuit
supplying a specific power rating. There are generally +3.3V, +5V, +12V
rails which are technically independent inside the power supply, many
cheaper designs have them sharing some circuitry, making them less
independent than they should be. This can cause voltage regulation
problems in which a significant load on one rail causes a voltage drop
on others. Components such as processors and graphic cards can vary
their power consumption greatly by their activity. When you suddenly
load a graphics intensive game, it causes the processor as well as the
video card to more than double the power consumption on the +12V rail
which powers them. In these cases, cheaper power supplies can cause
voltage fluctuations causing the system to crash. Better designed power
supplies feature independent rails with better regulation and better
quality wires to draw power from the rails.

Active PFCs

Most switched-mode power supplies with more than 75 W of output power
must include passive PFC, at least. 80 PLUS power supply certification
requires a power factor of 0.9 or more. Where power factor is purity of
the DC voltage obtained, here 1 power factor means it is completely
pure. An “active power factor corrector” (active PFC) is a power
electronic system that controls the amount of power drawn by a load in
order to obtain a power factor as close as possible to unity. The
purpose of making the power factor as close to unity as possible is to
make the load circuitry that is power factor corrected appear purely DC
and this ensures proper working of the internal components of the PC and
its longevity.
It is frequently used in practice, for example, SMPS with passive PFC
can achieve power factor of about 0.7–0.75, SMPS with active PFC can
supply up to a 0.99 power factor, while a SMPS without any power factor
correction has a power factor of only about 0.55–0.65. Due to their very
wide input voltage range, many power supplies with active PFC can
automatically adjust to operate on AC power from about 100 V to 230 V.
So it is always necessary to look out for PSUs with active PFCs.
So now that you know the basics of power supply units, go get
yourself the right one if you are still using cheap PSUs which can cause
potential harm to your system. The best way to decide on a PSU is to
calculate the power requirement for your system and then zeroing in on a
particular brand or model by searching their reviews on the net.